Apple (Mac OS X) has a relatively larger number of desktop computer users compared to Linux, and Windows virtually dominated the overall market share. But have you ever wondered why people at Microsoft and even Bill Gates himself are bothered by Linux more than anything else? I think here are the main reasons why:

1. Portability

There's no doubt that Linux is a highly flexible operating system that can be easily modified to run on just about any electronic device. Meanwhile, Apple's Mac OS X is tightly locked on its own hardware so I don't see its growth as long-term. I believe there will come a time that a Linux-powered computer or gadget becomes immensely popular, and Microsoft's dominance will be endangered.

2. Cost

I know it's hard to promote a product that costs nothing. But in these difficult times people have learned to value their money more than ever by spending it wisely. Linux sure is free but its capability is valuable.

3. Security

Windows is still the most insecure OS and it is possible that another devastating virus will strike and harm computers running with it. With Linux getting better like becoming user-friendlier and more secure than ever, people have a savior.

4. Firefox

Since Firefox has been rapidly eating Internet Explorer's web browser market share, the free and open source software community is more positive than ever that Linux can be as successful on the desktop. Microsofties are aware of this and are doing everything they can to stop the growth of Firefox and in effect Linux.

5. Applications, applications, applications

The number of great FOSS applications that support Linux are increasing. In terms of quality, they can rival any proprietary software made for Windows. Nowadays, it’s like if you can do it on Windows, you can do it on Linux too.

The year of the Linux desktop is unknown, but the future is bright. Indeed the good people at Microsoft have reasons to be afraid, or shall I say be very afraid of Linux :-)